Tri-color kinescope beam convergence system



Dec. 20, 1955 Filed July l, 1955 M. D. NELSON TRI-COLOR KINESCOPE BEAMCONVERGENCE SYSTEM 2 Sheets-Sheet 1 .SVG/vgl. ifm/V56 VFT/L'IL 5 WEE?VCL? Hoe/MMM VEB 77692 5 WEE? ffy-f IN I/EN TOR.

Marlis D. Nelson n RNE? Dec. 20, 1955 M D, NELSON 2,728,023

TRI-COLOR KINESCOPE BEAM CONVERGENCE SYSTEM Filed July 1, 1955 2Sheets-Sheet 2 ra Fan/.s Avans: zg, 25,24

INI/ENTOR.

Morris B11761501] /I RNEY TRI-COLOR KINESCOPE BEAM CONV ERGENC SYSTEMMorris D. Nelson, Bronx, N. Y., assignor to Radio Corporation ofAmerica, a corporation of Delaware Application July 1, 1953, Serial No.365,331

9 Claims. (Cl. 315-13) This invention relates to systems for controllingthe electron beam energy of cathode ray tubes. It pertains particularlyto the control of a plurality of electron beam components used intelevision kinescopes so as to eiect substantial convergence of the beamcomponents at all points of a raster scanned at a target electrode.

One type of cathode ray tube in which there is encountered the problemof maintaining substantial convergence of a plurality of beam componentsat a target electrode is a color kinescope such as `that' disclosed in apaper by H. B. Law titled A three-gun shadow-mask color kinescopepublished in the Proceedings of the I. R. E., vol. 39, No. 10, October1951 at page 1186. Such a tube has a luminescent screen consisting ofamulti plicity of phosphor areas of sub-elemental dimensions.

Diiferent ones of the phosphor areas are capable of pro-v ducing lightof the component imageV colors when excited i by electron beam energy.In this tube, the different lightproducing phosphor areas are` excitedrespectively by a plurality of electron beams, or by a plurality ofcomponents of a single beam, approaching the screen from diiferentangles through an apertured electrode. Color selection is secured by theangle at which `the electron beam components approach the screen. A tubeof the kind described forms the subject matter of U. S. Patent 2,595,548granted May 6, 1952, to Alfred C. Schroeder for Picture ReproducingApparatus.

The expression electronbeam components as used in this specication andclaims will be understood to denote the phosphor-exciting electronicenergy produced either by a single, or by a plurality of, electron guns.This energy may be continuous or pulsating as required without departingfrom the scope of the invention. An example of a color kinescope inwhich different components of a single electron beam are used to excitea phosphor screen of the kind described is disclosed in a paper by R. R.Law, titled A one-gun shadow-mask color kinescope published in theProceedings of the I. R. E., vol. 39, No. l0, October 1951, at page1194. Such a tube forms the subject matter of a copending U. S.application of Russell R. Law, Serial No. 165,552, filed June l, 1950and titled Color Television.

The successful operation of a multi-color kinescope of the type referredto requires that the plurality of` electron beam components be made toconverge substantially at the apertured electrode at all points in thescanned raster. In view of the fact that the dierent points of such atarget electrode are at diiferent distances from the point or region ofthe electron beam deection, it is necessary Beam Control System. In thesystem proposed by Friend, electron-optical apparatus is energized bothstatically and dynamically to produce the desired result. By meansincluding the static energization of the e1ectronoptical apparatus, theFriend system eifects initial convergence of the electron beam coponentssubstantially at the center of the raster to be scanned. The dynamicenergization of the electron-optical apparatus is effected as functionsof both the horizontal and vertical beam deflection. Ideally thesefunctions Vare parabolic. However, it is somewhat diicult to produce theideal energizing` waveforms, particularly at the vertical deectionfredeilection apparatus, waveforms for effecting dynamic convergence ofthe electron beam components of a multibeam kinescope.

ln accordance with this invention, there is provided a convergencecontrol wave-generating apparatus including a wave-shaping networkhaving a plurality of branches. Oppositely phased, substantially similarsawtooth waves at one of the deflection frequencies are impressed upontwo constituent wave branches of the network. The network also includes`an integrating branch which is coupled to at least one of theconstituent wave network branches so as to produce a substantiallyparabolic wave which may be derived from the integrating network branch.The integrating network branch may be coupled to both constituent wavenetwork branches in a manner to combine either polarity of a sawtoothwave with the parabolic wave.` The convergence control wave thusproduced is basically of parabolic form and may have a sawtoothcomponent if desired.

The novel features that are considered characteristic of this inventionare set forth with partcularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional objects and advantages thereof, will best beunderstood from the following description when read in connection withthe accompanying drawings.

In the drawings:

Figure 1 is a block diagram of a representative form of apparatus withwhich the present invention may be employed; i

Figure 2 is a schematic circuit diagram of an illustrative form of aconvergence control wave-generating apparatus Y 2in accordance with theinvention; and,

to provide a field-producing means which is variably energized toproduce the desired dynamic convergence control. One such electron beamcontrol system is disclosed in a paper by Albert W. Friend titledDeilection and convergence in color kinescopes published in the prov No.164,444, filed May 26, 1950 and titled Electron Figure 3 shows a seriesof curves illustrating dilferent kinds of convergence control waveformswhich may be produced by apparatus in accordance with the invention.

Reference first will be made to Figure 1 of the drawings for adescription of an illustrative embodiment of the invention. Thetelevision receiver represented in this figure is generally conventionaland includes an antenna 11 to which is coupled a conventional televisionsignal receiver 12. It will be understood that the receiver 12 may`include such usual apparatus as carrier wave ampliiers at both radioand intermediate frequencies, a frequency converter and a carrier wavedemodulator or signal i Accordingly, it will be understood that thereA12 are impressed upon a video signal channel 13 and the synchronizingsignals are impressed upon a sync signal separator 14. The video .signalchannel is coupled to the usual electron beam control apparatus,customarily referred to as electron gun apparatus, f all. irl@ege-repre`dncing device such as a kinescope 15.

ln the illustrative embodiment of the invention, it is assumed that theinvention is used in a color television' system. ln this case, thekinescope is of the same general type disclosed in the` H. B.. Law paperpreviously referred to. It will be understood, however, that thekinescope alternatively may be of other types such as that shown in theaforementioned R. R. Law paper. In either case, however, the kinescopehas a subsantially flat luminescent screen 16 which is provided with amultiplicity of small phosphor areas arranged in groups and capablerespectively of producing light of the different primary colors in whichthe image is to be :reproduced when excited by electron beam energy. Inback of, and spaced from the screen 16, there is an apertured maskingelectrode 17 having .an aperture for, and in alignment with, each groupof phosphor areas of the screen 16. In the particular tube illustrated,the kinescope also has a plurality of electron guns 18, 19 and 20.,equal in number to the number of primary colors in which the image is tobe reproduced. As previously indicated, these three electron guns arecoupled to the video signal channel 13 for respective control by videosignals representing the three primary colors in which the image is tobe reproduced. It will be understood that each .of these guns may beconventional consisting of a cathode, a control grid, and a first anode,or beam-forming electrode. Also associated with the three electron gunsare corresponding individual beam-focusing anodes 22, 23 and 24. Thethree electron guns 18, 19 and Ztl, together with their associatedfocusing electrodes 22, 23 and 24 respectively, function to developrespective electron beams 25, 26 and 27 which are caused to approach thetarget electrode structure, including the luminescent screen 16 and themasking electrode 17, from three different angles which, forconvenience, have been shown greatly exaggerated in the drawing. Byrmeans of the different angles of approach these beams are caused toexcite the different colored light-producing phosphors.

The color kinescope additionally is provided with an electro-static typeof beam-converging apparatus which includes a convergence anode 28located adjacent the paths followed by the electron beams in thepredeflection region. The kinescope also includes the usual final, orbeam-accelerating, anode 29 generally in the form of a wall coatingsubstantially as shown and extending from the predeflection regionadjacent to the convergence anode 28 to the vicinity of the targetelectrode structure including the screen 16.

The different static potentials which are impressed upon the variouskinescope electrodes are derived from a power supply 31, across theterminals of which is connected a lvoltage divider resistor 32. Thevarious electrode potentials are derived by making suitablelconnectionsto the voltage divider resistor generally in the manner shown. Theindividual beam-focusing electrodes 22, 23 and 24 are connected together'with and to a relatively low positive potential point on the voltagedivider resistor 32. The convergence anode 28 is coupled to a somewhathigher positive potential point of the resistor 32 so that, as a resultof the potential difference between it and the individual beam focusinganodes 22, 23 and 24, there are produced electrostatic clectron'opticallenses by which individual beam focusing is effected.' In a like manner,the final anode 29 is connected to a relatively high positive potentialpoint on the voltage divider resistor 32 so as to create anotherelectron-optical lens with the convergence anode 2S. The purpose of thislatter electron-optical device is to produce the desired convergence ofthe individual electron beams substantially in the plane of theapertu-red electrode 17.

The color kinescope 15 also is provided with apparatus by which todeflect the plurality of electron beam components both vertically andhorizontally to scan the usual raster at the luminescent screen 16. Inthis embodiof the tube.

signals respectively in its output circuits H and V.

ment of the invention the deflection apparatus includes a yoke 33 whichin general is of a conventional type. It consists of a pair ofinterconnected coils forming a horizontal deection winding and anotherpair of coils forming a vertical deflection winding. The yoke is mountedaround the neck of the kinescope in the region adjacent to the point atwhich the neck joins the conical section The horizontal and verticalwindings of the yoke 33 are energized by substantially conventionalapparatus. The sync signal separator 14, which separates the syncsignals from the video signals and from one another, produces horizontaland vertical frequency sync The horizontal output circuit H is coupledto a horizontal sweep oscillator 34, the output of which, in turn, iscoupled to the input circuit of a horizontal sweep output apparatus 35.Both of these horizontal sweep com- 'ponents may be entirelyconventional. The output circuit of the horizontal sweep outputapparatus 35 is coupled to the horizontal deflection winding of the yoke33 in the customary manner.

The vertical sync separator output circuit V is coupled to a verticalsweep oscillator 36 which produces at its output terminal 37 asubstantially sawtooth deflection wave 38 at the vertical deflectionfrequency. The output of the vertical sweep oscillator is coupled to theinput circuit of a vertical sweep output stage 39 having an outputterminal 40 at which a sawtooth deflection wave l1 is developed. Thekoutput circuit of the vertical sweep output apparatus is connected tothe vertical deflection Winding of the yoke 33.

In order to effect the desired convergence of the electron beamcomponents of the tri-color kinescope 15 at both horizontal and verticaldeflection frequencies, a substantially sawtooth wave 42 at horizontaldeflection frequency is impressed upon a horizontal convergence controlwave generator 43. This apparatus may be substantiallyy of the typedisclosed in the Friend paper previously referred to. However, ifdesired, it may be of the same general type, with suitable modificationsfor the particular operating frequency, as a generator in accordancewith the present invention. In any case, it will be understood that thehorizontal convergence control wave generator functions to produce asubstantially parabolic convergence control wave 44 at the horizon-taldeflection frequency. Such a wave is impressed upon the primary windingl5 of a convergence control wave output transformer 46. The secondarywinding 47 of this output transformer is coupled by means including thecapacitor 48 to the convergence control anode 28 of the tri-colorkinescope 15.

The substantially sawtooth deflection wave 38 and 41 at verticaldeflection frequency derived respectively lfrom terminals37 and 40 areimpressed upon input terminals 49 and 50 of a vertical convergencecontrol wave generator 51. An illustrative form* of this generator is inaccordance with the present invention and will be described in detailpresently. it will be understood that the vertical convergence controlwave generator 51 functions to produce a substantially parabolic wave S2at an output terminal 53. This wave is combined with the convergencecontrol wave 44 at the horizontal deflection frcqueney by coupling theyterminal 53 to the secondary winding 47 of the output transformer 46.

Reference now will be made to Figure 2 of the drawings for a descriptionof an illustrative form of the pre:- ent invention. The substantiallysawtooth deflection wave 3S, which is developed at the output terminal37 of the vertical sweep oscillator for employment as the drivingvoltage for the vertical sweep output 39, usually is developed across.such a circuit as one including a resistor 54 and a capacitor 55. Thedeflection ,wave 5I/3 includes a, sawtooth component 5.6 and a peakingconi- POlnt 5 1. The `peaking component is developed across the resistorS4 and the sawtooth component is developed across the capacitor 55. By"coupling to the capacitor 55, only the sawtooth component 56 of thedeection wave 38 is impressed upon a capacity type of voltage dividerincluding capacitors 58 and 59. By means of such an arrangement, anadjustmentof one circuit does not disturb the operation of another o'neof the circuits coupled to the output of the vertical sweep oscillator36 of Figure 1. In this manner, a sawtooth wave 60 is 'impressed uponthe input circuit of a triode electron tube 61. The input sawtooth Wave60 is converted by means including this tube into an output constituentsawtooth wave 62 of negative polarity. It also is to be noted that thereformed constituent wave 62 does not include the peaking pulses of thedeflection sawtooth wave 38.

The vertical sweep output apparatus includes an electron tube 63 whichfunctions in the usual manner to couple the substantially sawtooth wave38 to the output terminal 40 by means including an output transformer64. As indicated in this iigure and also in Figure l, the substantiallysawtooth wave 41 so developed is impressed upon the deection yoke 33 ofthe tri-color kinescope 15 of Figure l.

The deflection sawtooth wave 4 which is impressed upon the inputterminal 50 of the vertical convergence control wave generator 51 ofFigure l has the peaking component clipped therefrom by means includinga unilaterally conducting device such as a crystal diode 65 connected inseries with the anode supply voltage for the tube 6l, resistors 66 and67 and a capacitor 68. By such means, there is `impressed upon oneterminal of a signal mixing potentiometer 69 a substantially reformedconstituent sawtooth wave 70 of positive polarity. As previouslydescribed, the negative constituent sawtooth wave 62 is impressed bymeans including a series resistor 71 upon the other terminal of thepotentiometer 69.

There also is connected in parallel with the series arrangement of thepotentiometer 69 and the resistor 71 another potentiometer 72 acrosswhich there is developed a sawtooth wave which is integrated by meansincluding the potentiometer 72, a resistor 73 and a capacitor 74,whereby to produce a substantially parabolic wave 75 which is impressedupon the input circuit of an output tube 76. rThe potentiometers 69 and72, together with such other apparatus as the resistor 69 and thecapacitor 70, `comprise a wave-shaping network. Accordingly, thesubstantially parabolic Wave 52 is developed at the output terminal 53.

The interconnection of the potentiometers 69 and 72 by means of thecircuit which includes the integrating network comprising the resistor73 and the capacitor 74 enables a suitable mixture of the sawtooth andparabolic wave components to produce the desired convergence controlwave. The amplitude of such a wave, which is essentially parabolic, iscontrolled by means of the potentiometer 72. An adjustment of thepotentiometer 69 effects the combination with the parabolic wave of asawtooth wave component of either polarity and of any desired amplitude.Such a facility is seen to be available by virtue of the fact that theconstituent sawtooth waves 62 and 70 respectively of opposite polarityare impressed upon opposite terminals of the potentiometer 69 asdescribed.

In order to avoid the use of a convergence control wave outputtransformer for the purpose of producing a convergence control wave ofsufficient amplitude, the anodeof the convergence control wave outputtube ".76 is provided with a suitable voltage supply by a connection toa Voltage divider or bleeder network including a i series connection ofresistors 77, 78 and 79 connected between terminals 80 andSl. There isimpressed upon the terminal 80, for example, a potential ofapproximately 700 volts which may be conveniently derived from vtheboosted B supply usually available in the horizontal deflection outputcircuit. Such a power supply is commonly used and may be in accordancewith tion System. The terminal 81 may also have impressed thereon ahigher positive potential of the order of 3500 volts, for example. Sucha voltage may be provided somewhat in the usual manner by means of aflyback high voltage power supply such as that shown in U. S. Patent2,074,495 granted March 23, 1937, to A. W. Vance and titled Circuits forCathode Ray Tubes. It has been determined that the point on the voltagedivider to which the anode of the tube 76 is connected has a voltage ofapproximately 1300 volts when the tube 76 is cut off. During theintervals of current conduction in the tube 76, the anode voltage maydrop to approximately ground potential because of the relatively largevalue of the load resistancewhich, in the circuit indicated in thedrawing, is effectively 1.8 megohms. As indicated, the resistor 79 ofthe Voltage divider may be in the form of a potentiometer, theadjustable contact of which is connected to the focusing anodes such as22, 23 and 24 of Figure l, as indicated.`

Figure 3 illustrates three typical types of convergence controlwaveforms which may be obtained by use of apparatus such as thatdescribed embodying the invention. The wave 82 is one which issubstantially all parabolic in form. The setting of the potentiometer 69is such that no sawtooth wave component is included. The wave 83 is onewhich is made up of a parabolic component such as the wave 82 to whichis added a sawtooth wave component of positive polarity. The wave 84 isa parabolic wave to which a negative sawtooth component has been added.It is seen that the wave 82 is of a symmetrical form in any one cyclethereof, whereas the wave 83 is effectively tipped toward the left, asviewed in the drawing, and the wave 84 is tipped toward the right.

Thus, it may be seen that the present invention provides apparatus of arelatively simple character which materially reduces the cost ofequipment necessary to generate a beam convergence control wave. VIt isseen that such apparatus requires only a resistance coupled amplierwhich may be operated from the available B-isupply. It, therefore, isunnecessary to employ an output transformer for the purpose ofincreasing the amplitude of the convergence control wave. Not only issuch transformer apparatus relatively costly, particularly for operationat eld deflection frequency, but also it tends to distort theconvergence control waves from the desired form, thereby requiringadditional apparatus by which to compensate for such distortion.

Having described an illustrative embodiment of the invention, its scopeis pointed out in the appended claims.

What is claimed is:

l. In a cathode ray image reproducing system wherein a plurality ofelectron beam components, which traverse predeection paths that arespaced respectively about the longitudinal axis of a tube, are angularlydeliected both horizontally and vertically to scan a raster and havingfield-producing means adjacent to said predeection paths and energizableto effect substantial convergence of said beam components at all pointsof said raster, a system to energize said field-producing meanscomprising, a convergence control wave-shaping network including aplurality of branches, means to produce first and second constituentsawtooth waves of opposite polarity and having one of said deilectionfrequencies, means coupling said constituent wave-producing means tosaid Wave-shaping network in a manner to impress said first and secondconstituent sawtooth waves respectively upon two constituent wavebranches of said network, means including an integrating branch of saidnetwork coupled to one of said constituent wave network branches tointegrate one of said constituent sawtooth waves into a substantiallyparabolic waveform, and means coupled to said integrating network branchto derive therefrom said convergence control wave for application tosaid field-producing means,

2. In a cathode ray image reproducing system wherein a plurality ofelectron beam components, which traverse predeflection paths that arespaced respectively about the longitudinal axis of a tube, are angularlydeflected both horizontally and vertically to scan a raster and havingfield-producing means adjacent to said predeflection paths andenergizable to effect substantial convergence of said beam components atall points of said raster, a system to energize said field-producingmeans comprising, a source of a substantially sawtooth raster-scanningdeflection wave, a convergence control wave-shaping network including aplurality of branches, means coupled to said sawtooth wave source toproduce first and second constituent sawtooth waves of opposite polarityand generally similar in shape to said deflection wave, means couplingsaid constituent wave-producing means to said waveshaping network in amanner to impress said first and second constituent sawtooth wavesrespectively upon two constituent wave branches of said network, meansincluding an integrating branch of said network coupled between said twoconstituent wave network branches to integrate one of said constituentsawtooth waves into a substantially parabolic waveform, and meanscoupled to said integrating network branch to derive therefrom saidrconvergence control wave.

3. In a cathode ray image reproducing system wherein a plurality ofelectron beam components, which traverse predeflection paths that arespaced respectively about the longitudinal axis of a tube, are angularlydeflected both horizontally and vertically to scan a raster and havingfield-producing means adjacent to said predeflection paths andenergizable to effect substantial convergence of said beam components atall points of said raster, a system to energize said field-producingmeans comprising, a source of a substantially sawtooth raster-scanningdeflection wave, a convergence control wave-shaping network includingtwo branches, means coupled to said sawtooth wave source to produce afirst constituent sawtooth wave of predetermined polarity and generallysimilar in shape to said dellection wave, means coupling said firstconstituent waveproducing means to said wave-shaping network in a mannerto impress said first constituent sawtooth wave upon both of saidnetwork branches, means coupled to said deflection wave source toproduce a second constituent sawtooth wave similar in shape to saidfirst constituent sawtooth wave but of opposite polarity, means couplingsaid second constituent wave-producing means to said wave-shapingnetwork in a manner to impress said secondl constituent sawtooth waveupon both of said network branches, means coupled between said networkbranches in a manner to integrate one of said constituent sawtooth wavesinto a substantially parabolic waveform, and means coupled `to saidwave-shaping network to derive therefrom said convergence control wavefor application to said field-producing means.

4. In a cathode ray image reproducing system wherein a plurality ofelectron beam components, which traverse predeflection paths that arespaced respectively about the longitudinal axis of a tube, are angularlydeflected both horizontaliy and vertically to scan a raster and havingfield-producing means adjacent to said predeflection paths andenergizable to effect substantial convergence ot said beam components atall points. of said raster, a system to energize said field-producingmeans comprising, a source of a substantially sawtooth raster-scanningdeflection wave, a convergence control wave-shaping network includingtwo predominantly resistive branches, an electron tube having an inputcircuit and an output circuit, means coupled between said sawtooth wavesource and said input circuit to impress a predetermined portion of saiddeflection wave upon said tube, saidielectron tube being operated insuclra manner as to produce in said output circuit a first constituentsawtooth wave of predetermined polarity and generally similar in. shapeto said deflection wave, means coupling said outputcircuit to saidwave-shaping network in a manner to impress said first constituentsawtooth wave upon respective points of said resistive branches, meanscoupled to said deflection wave source to produce a second constituentsawtooth wave similar in shape to said first constituent sawtooth wavebut of opposite polarity, means coupling said second constituentsawtooth wave-producing means to said waveshaping network in a manner toimpress said second constituent sawtooth wave upon other respectivepoints of said resistive branches, means coupled between still otherpoints of said resistive branches in a manner to integrate one of saidconstituent sawtooth waves into a substantially parabolic waveform, andmeans coupled to said integrating means to derive therefrom saidconvergence control wave for application to said field-producing means.

5. In a cathode ray image reproducing system wherein a plurality of'electron beam components, which traverse predellection paths that arespaced respectively about the longitudinal axis of a tube, are angularlydeflected both horizontally and vertically to scan a raster and havingfield-producing means adjacent to said predeflection paths andenergizable to effect substantial convergence of said beam components atall points of said raster, a system to energize said field-producingmeans comprising, a source of a substantially sawtooth raster-scanningdeflection wave having a peaking component, a convergence controlwaveshaping network includingy two resistive branches, an electron tubehaving an input circuit and an output circuit, voltage dividing meanscoupled between said sawtooth wave source and said input circuit toimpress a predetermined portion of said deflection wave upon said tube,said electron tube being operated in such a manner as to produce in saidoutput circuit a first reformed sawtooth wave of predetermined polarityand generally similar in shape to said deflection wave with said peakingcornponent removed, means coupling said output circuit to saidwave-shaping network in a manner to impress said first reformed sawtoothwave upon corresponding points of said resistive branches, meanscomprising a clipping circuit including a uni-laterally conductingdevice coupled` to said deflection wave source to remove said peakingcomponent from said deflection wave whereby to produce a second reformedsawtooth wave similar in shape to said first reformed sawtooth wave butof opposite polarity, means coupling said clipping circuit to saidWavesliaping network in a manner to impress said second reformedsawtooth wave upon other corresponding points of said resistivebranches, means coupled between points of said respective resistivebranches in a manner to integrate one of: said reformed sawtooth wavesinto a substantially parabolic waveform, andV means coupled to saidintegrating means to derive therefrom said convergence control Wave forapplication to said field-producing means.

6. In a cathode ray image reproducing system wherein a plurality ofelectron beam components, which traverse predeflection paths that arespaced respectively about the longitudinal axis of ay tube, areangularly deflected both horizontally and vertically to scan a rasterand having field-producing means adjacent to said predeflection pathsand energizable to effect substantial convergence of said beamcomponents at all points of said raster, a system to energize saidfield-producing means comprising, a source of a substantially sawtoothraster-scanning deflection wave having a peaking component, aconvergence control waveshaping network including two parallel-connectedresistive branches, an electron tube having an input circuit and anoutput circuit, means including a voltage divider coupled between saidsawtooth wave source and said input circuit to impress a predeterminedportion of said deflection wave upon said tube, said electron tube beingoperated in such a manner as to produce in said output circuit a firstreformed sawtooth wave of predetermined polarity and generally similarin shape to said deflection wave said output circuit to one terminal ofsaid wave-shaping network to impress said iirst reformed sawtooth waveupon corresponding ends of said resistive branches, means including anoutput transformer coupled to said deection wave source for impressingsaid deiiection wave upon said raster-scanning deflection apparatus,means comprising a clipping circuit including a unilaterally conductingdevice and a resistive-capacitive network coupled to said deflectionoutput transformer to remove said peaking component from said deflectionwave whereby to produce a second reformed sawtooth wave similar in shapeto said first reformed sawtooth wave but of opposite polarity, meanscoupling said clipping circuit to the other terminal of saidwave-shaping network to impress said second ref formed sawtooth waveupon the other corresponding ends of said resistive branches, meansincluding an integrating network coupled between points of saidrespective resistive branches to integrate one of said reformed sawtoothWaves into a substantially parabolic waveform, and means coupled to saidintegrating network to derive therefrom said convergence control wavefor application to said fieldproducing means.

7. ln a cathode ray image reproducing system wherein a plurality ofelectron beam components, which traverse predeilection paths that arespaced respectively about the longitudinal axis of a tube, are angularlydeflected both horizontally and vertically to scan a raster and havingheld-producing means adjacent to said predeiiection paths andenergizable to effect substantial convergence of said beam components atall points of said raster, a system to energize said field-producingmeans comprising, a source of a substantially sawtooth raster-scanningdelieetion wave having a peaking component, a convergence controlwave-shaping network including two parallelconnected branches, eachincluding a potentiometer, an electron tube having an input circuit andan output circuit, means including a capacity voltage divider coupledbetween said sawtooth Wave source and said input circuit to impress apredetermined portion of said deflection wave upon said tube, saidelectron tube being operated in such a manner as to produce in saidoutput circuit a first reformed sawtooth wave of predetermined polarityand generally similar in shape to said deflection wave with said peakingcomponent removed, means coupling said output circuit to one terminal ofsaid wave-shaping network to impress said first reformed sawtooth waveupon corresponding ends of said potentiometers, means including anoutput transformer coupled to said deection wave source for impressingsaid deiiection wave upon said raster-scanning deliection apparatus,means comprising a clipping circuit including a crystal diode and aresistive-capacitive network coupled to said deflection outputtransformer to remove said peaking component from said deection wavewhereby to produce a second reformed sawtooth wave similar in shape tosaid first reformed sawtooth wave but of opposite polarity, meanscoupling said clipping circuit to the other terminal of vsaidwave-shaping network to impress said second reformed sawtooth wave uponthe other corresponding ends of said potentiometers, means including aresistive-capacitive integrating network coupled between saidpotentiometers to integrate one of said reformed sawtooth waves into asubstantially parabolic waveform, and means coupled to said integratingnetwork to derive therefrom said convergence control wave forapplication to said eldproducing means.

8. A convergence control wave-generating system as defined in claim 7wherein, the peaking component of said deflection wave has anegative-going polarity, and said crystal diode is serially connected insaid tube output circuit.

9. A convergence control wave-generating system as defined in claim 7wherein, said integrating network includes a series arrangement of aresistor and a capacitor, said resistor being connected to theadjustable contact of one of said potentiometers, the adjustment of saidone potentiometer contact determining the amplitude of said convergencecontrol wave, and said capacitor being connected to the adjustablecontact of the other of said potentiometers, the adjustment of saidother potentiometer determining the amplitude and polarity of anysawtooth wave component combined with said parabolic wave to form saidconvergence control wave,

References Cited in the file of this patent UNITED STATES PATENTS

